Community maps are possible, you can't copy paste but you can reduce the size of a map to what you want to use. It's basically how master maps are right now. Maps that large are incredibly hard to make detailed however, mostly because as you build more and more elevation data into the map the editing process grinds to a halt as the game re-calculates every. single. point.
Well it kind of resembles the cliffs in Dinant... which is kind of in the Ardennes! Would probably make an interesting "what-if" scenario...

Building off Bulletpoint, I think the aspect of having to make a less then perfect decision amplifies that satisfaction even more. The terrain of a map plays a huge role in this, because it is the one thing you have no influence over. Real life commanders never had the perfect support by fire position or covered routes into the enemies rear, they had to deal with the hand their were dealt, both on offense and defense. The terrain was as much of an enemy sometimes as the man on the pointy end of your rifle. It's why the first step of almost any military planning process is to analyze the terrain. The great captains of military history are as renowned for their ability to read the ground just as much as their ability to lead men. "Terrain walks" are a staple of any military staff ride. All this to say that when you "bake in" terrain, you are taking away a big chunk of the decision making process. When you bake in these convenient support by fire positions, the decision is no longer "where on this map should I place my support by fire position?", but instead "should I go to Position A, B or C?". On a "natural" map, maybe there is no tenable support by fire position. The player must adapt. Maybe they utilize more of their artillery up front to compensate. Or choose to utilize a smoke screen. Or one of a hundred other ways a player can utilize the terrain and their understanding of tactics to achieve their mission. Offering up a player a series of built in options is no longer a tactical game, but a "choose your own adventure". It's why I'm deeply dissatisfied with games like the new X-Com or Unity of Command - the game offers up to you a series of baked in options, of which only a few actually work.
Another factor of tactical appeal is that the closer a map is to realistic terrain, the more likely you are to utilize realistic tactics. Half the fun of Combat Mission is pretending you're a WW2 commander and understanding why they made the decision they did.
Check out combatintman's excellent play through of one of my scenarios here: http://community.battlefront.com/topic/120527-no-plan-survives-first-contact-with-the-enemy-planning-tutorial/
He dives deep into an excellent analysis of the terrain I provided and builds a plan that I never even envisioned while designing the scenario. That's exciting! That's what real commanders had to do! Not solving a puzzle the designer offered up to you. Later in that thread I also talk about how I designed the map and more about my philosophy on scenario design.
As for why sometimes *too* realistic is a bad thing, I imagine a faithful re-creation of Ardennes style woods would result in little decision making beyond putting your soldiers in a line and waiting until they step on a mine or take a bullet to the face from 15m away. Realistic terrain yes, but not very fun. Also, a personal pet peeve of mine - zig zag roads. Yes, the "real thing" has a road branching straight off at a 67.76 degree angle from the main junction, but if I try to replicate that in Combat Mission with the draw tool, it will create a mess of zig zaggy road sections. If you now try to put a hedge or forest along that road, it will inevitably create a break in LOS on what is, in real life, an arrow straight road that just happens to branch off at a weird angle. The resulting CM recreation looks odd and often plays odd.

Try my CMRT "Assault Position" and "Pastureland" for examples of how open fields can be tweaked to create interesting tactical situations! Pastureland takes place pretty much entirely in an "open" field. The only cover you have is the folds you find in the terrain.
Also check this out: https://www.dropbox.com/home/Public?preview=AD+Waldbillig+Waltz.btt
It's a scenario I was never able to get over the goal line due to other commitments, but I think it's probably one of my better maps. It has the size and terrain you are looking for and is based heavily off the real thing.
Also, re:frontages again. Remember that the entire company was not on line, and these companies could often be at 50% strength if they've been in heavy combat. These companies may only have a platoon up, and that platoon may only be 25 dudes. That stuff is lost in translation sometimes.

On elevations, I will say don't be afraid to create that dead ground. Hike through the hills and you'll see dead space is a common issue defending units would have to deal with in real life. Going out of your way to create clear lines of sight creates the tabletop gaming look you are actually trying to avoid. Natural hills have undulations and numerous draws and spurs that create difficulties for the defender and opportunities for the attacker. I don't think any attacking infantry force would ever have taken a hilltop defensive position if those natural dead spaces didn't exist in real life. You'd be surprised at how nuanced and "stepped" terrain can be in real life. I've found the best way to construct realistic elevations is to draw your contour lines fairly spread out (10 or 15m in elevations) and then using the "Adjust" tool set to 1m to add variation. This creates the natural folds you are looking to re-create, adding micro terrain infantry can utilize.
I go to great lengths to try to re-create the real world in CM, and many of the things you discuss about here concern me as well. Check out some of my scenario maps to see how I deal with them. I put an extraordinary amount of time into my elevations and villages.
Also on the subject of infantry frontages, attacking infantry forces would absolutely stick to cover. Defensive lines weren't literal lines of men occupying every piece of ground, instead clustering and flowing around the terrain that is actually defensible. Vast open ground could easily be covered by artillery and machinegun fire, and often didn't serve a purpose anyway. Roads have always been the key to warfare and defenses were focused around those key avenues of approach. Even a "hilltop defense" was key only because it overlooked an avenue of approach needed by the attacker to continue their offensive. Your map may be 1.5km wide but not every piece of ground on that map is key terrain the defender would occupy or even care about. A 1.5km map would probably support an attacking infantry battalion with 2 companies up 1 back against a company sized defending force.
Check out the US Army Green Books, they provide a history of the US Army in WW2 in all theaters, and have excellent maps sometimes showing maneuver down to the company level. Gives a great picture on how WW2 armies actually fought and what they considered important.
Also, don't overly concern yourself with machinegun lines of fire - take a trip through Europe on Google Street view and see how rare it actually is to have long sight lines. Far too often vegetation and microterrain blocks line of sight over what would otherwise look like good ground. Remember, these machineguns are dug in at ground height! Go for a walk outside and when you think you've found a good position, lie down and see how much your opinion changes!

I'm going to offer my own, un-solicited advice on map making...
Use the light forest tile under trees, fences, hedges, roads, buildings, any sort of man-made "divider" - its represents well the undergrowth that builds up on these less traveled/less maintained areas. Look at pictures of rural fences and such and you'll see shrubbery/grass growing taller then the immediate surrounding foliage It also serves as an eye pleasing way to "break up" large chunks of terrain, especially when you're zoomed out - where most players actually play the game - and the fences start to blend in with the surrounding grass.
Alternate between yellow grass, tall grass, green grass, extra tall grass, etc when building large fields. Breaks up the color tone that looks unnatural when zoomed out. Same goes for dirt - mix in dirt, red dirt, hard dirt etc when building lots for your buildings. These large lots - either grass or dirt, or whatever - should look like a Jackson Pollock painting in the editor. Just splashes of different tiles everywhere.
Dirt footpaths serve as a great way to break up terrain as well - simulates the many different ways people cross fields, and the paths they create. Also works great in residential dirt lots.
Combine different buildings to make a realistic looking residence. I like to use the half tile barn on the end of an independent one story house. The half tile barns also look good between fences, and when they form an "L" at a 90 degree angle to a house.
Really pay attention to how homes are setup for the area you are modeling. They are often tighter and more "intimate" then you think. Remember, tiles are 8 meters by 8 meters, which is absolutely huge. I would say most Eastern European residential lots are maybe 3x3 or 4x3 in CM terms. Use street view when you can to see how they look from ground level. Satellite imagery can be deceiving.
When it comes to forests, less is more. I almost never use the two or three tile tree lots. Single trees are enough. In fact, drop your block of trees, and then go back and remove some trees from random tiles. Creates a realistic patchwork effect. Also, use different types of trees in a forest. Trees of the same type in CM are universal in height - no forest is like that in the real word. I like to use Tree D - a fairly short tree - and mix the taller A and C trees into the mix. Creates a more natural forest.
Avoid painting solid lines of height elevation. There is nowhere in this natural world where you have a universal flat area or a universally sloping area (bar maybe a salt bed, I guess..) Purposely leave gaps in your contour lines, and then drop random points in between contours that are one higher or one lower then what the game "calculates" it should be. It will create very pleasing, very natural, undulating terrain. Failing to do this is probably the biggest sin when it comes to map making in CM, in my mind. Elevation is much more difficult in CM2 then it was in CM1, which is why I think people have a hard time with this. But if you take the time to hand craft your elevations, it will pay off big. It makes your map look 100x more realistic.
Don't tie yourself to an overlay! The real world is much more angular then what CM can handle. Have fun with your map - no one will care if this street had 7 houses instead of 5. What matters is the look, and how it plays, Additionally, the height data in Google Earth and other public programs does not have the fidelity to make a realistic map. It's great for a starting point - ie, this town is on a hill - but the nuances of height elevation in real life terrain can not be captured in an overlay. Go for a walk and look for the micro terrain that is out there. Most of it is well within CM's ability to model.

@Kaunitz, don't stress the details man. No one is going to armchair quarterback the likelihood of the background for your scenario, because no one actually knows what would happen... The scenario you have is plausible. The enemy is guarding the woods, whether it be for recon purposes or to provide direct fire over a minefield, it doesn't truly matter. The enemy has their own reasons for being places and you can't understand it all the time. But the enemy is there. Your commander wants you to take it out. Maybe they are calling for fire on the decisive effort. Maybe the battalion commander really hates the idea of an enemy in your rear area. Maybe he's is drunk. Anything could happen, even in training nothing ever plays out the way our brilliant military masterminds expect it to, believe me on that one!! The enemy is there and they must die, that's all that matters to the players.
If you are worried about play balance, I can tell you that 2:1 in favor of the player is a good ratio for an attack. So you can do two friendly platoons with APCs or IFVs, vs one reduced enemy platoon, whio are sans vehicles but with guided ATGMs. That would make a balanced scenario. Take away vehicles or raise the casualty percentages in the editor to get the numbers closer, if needed. Easiest way to justify changes to the TOE is casualties or hasty field substitutions... just because big Army doesn't think your troops need RPG 7s, doesn't mean the ground commanders agree! The exact details (ie recon vs infantry, BMPs vs BTRs) of that force can be shaped by the background of your missions.

First - Combatintman, thank you for the plug, I appreciate the kind words.
Second - Kaunitz, if this is your first map, 2.5km x 4km is biting off way more then you can chew! Trust me on this one! You need to scale it back! 1000x1400 would be a much more suitable size for your engagement, and is much more manageable in the editor to boot.
The narrative you've built for your scenario is excellent. Just enough background detail to get the point across. The minefield is a very credible threat, severely impacting the ability for wheeled vehicles to use that avenue- maybe not worthy of a set piece attack, but enough of a concern to send a platoon to deal with it. This kind of stuff happened all the time in World War 2 and would happen in a modern conflict as well. Don't sweat the small stuff, that is easy to hand wave away. Don't have artillery support? Eh, it's busy elsewhere, you ain't important enough (as suggested above). Why not at night? Eh, timeline is too tight, war waits for no man.
Third - If you do end up cutting your map size down, I've attached a map with a red box around what I think is a suitable looking area you can cut out and model in game. Scenarios set in open farm land can be tricky as the extremely long sight lines can make it difficult to come up with credible attack plans. Having the main road, fence lines and what looks like a dry stream adds multiple avenues of approach for the player without "scripting" the scenario. It also makes setup of the defender more interesting as you have to account for all possible player choices! You can never get it 100% right, which is good. It's supposed to be a scenario, not a puzzle, IMO....
Another hint for map design... don't have your height map be based only on contour lines... add fixed height boxes of 1m difference between the lines to create more rolling terrain. The amount of realism (and tactical nuance) you can add by this one action alone is unbelievable! Download some of my maps, and you'll see what I mean. Also, paved roads and fence lines tend to be "built" up, and create natural barriers that troops can hide behind. Ditch lock these terrain features 1m higher then the surrounding ground and watch your map pop with detail... dirt roads and paths do the opposite, ditch lock those 1m down from the surrounding terrain. The number one thing that I believe makes maps look more realistic is this use of varying height. It can take a bland looking map and make it one that is full of realism.
Also, don't be afraid to change reality... Google Earth makes it easy to copy real locations, but sometimes that just ain't fun! I always use a blended approach of reality and my imagination.
Just my 2 cents of course, I am happy to see other scenario designers participating in this great hobby and don't want to discourage you! I hope you have fun!

With US artillery, assuming you've accounted for all non-standard conditions, you will still have a "beaten zone" or around 80-120m long and 40m wide. This for a point target, both in game and in real life. A while ago I did some tests, and the game results were actually quite similar to data pulled from the US TFTs for a range of around 12,000-15,000m. I had the exact data written down, but it's gone now. I don't know what your "beaten zone" looks like in this particular case but modern artillery isn't a sniper rifle.

Fall foliage is one of the hardest things for me to mod. I believe it has to do with the way the LODs are drawn in this game. At close distance, a multi-colored tree looks great and super realistic... but as soon as you back off and start actually playing the game, the LODs start kicking in and it's almost impossible to get the art to match color wise... and hence you get that super distracting POP as trees come in and out of LOD distance and the color changes. So I settled for the multi colored look by just giving every tree a different fall color.
The coloring for fall foliage is also extremely hard for me to get right... either the color is too bright and trees look like lollipops, or everything is too drab and it looks like plastic dipped in mud. Hopefully someone more skilled then I will come along and make a kickass fall foliage mod, because the more I play with the art, the more it looks worse.